Surface texture measuring instrument

ABSTRACT

A surface texture measuring instrument includes a force sensor ( 1 ), an actuator ( 11 ) and a detector ( 12 ). The surface texture measuring instrument further includes: a scanning controller ( 54 ) that collects a detection signal from the force sensor ( 1 ) and drives the actuator such that the detecting signal coincides with a target measurement value; a touch signal generator ( 51 ) that generates a touch signal when the detection signal from the force sensor ( 1 ) coincides with the target measurement value; and a measurement value collecting unit ( 55 ) that collects a measurement value from a counter ( 26 ) at a predetermined time interval in a state where a fluctuation range of the detection signal from the force sensor ( 1 ) is within a preset range when a scanning controller is in operation, the latch counter ( 52 ) collecting a measurement value from a latch counter ( 52 ) each time the touch signal is generated in a state where the detection signal from the force sensor ( 1 ) oscillates and an amplitude exceeds the preset range.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a surface texture measuring instrument.For example, the invention relates to a surface texture measuringinstrument that measures a surface texture such as a profile or surfaceroughness of a workpiece by an oscillation-type force sensor.

2. Description of Related Art

As a surface texture measuring instrument that scans a surface of aworkpiece and measures a surface texture such as a profile or surfaceroughness of the workpiece, a roughness measuring machine, a contourmeasuring machine, a roundness measuring machine, a coordinate measuringmachine and the like are known.

In the measuring machines, an oscillation-type force sensor is used as asensor for detecting a workpiece surface based on fine displacementcaused when a contact portion contacts the workpiece surface.

<Oscillation-Type Force Sensor>

As shown in FIG. 10, an oscillation-type force sensor 1 (a measuringportion) includes a metal base 2, a stylus 3 integrally formed with thebase 2, an oscillation element 4 that oscillates the stylus 3 (in anaxial direction of the stylus 3) and a detection element 5 that detectsan oscillation state of the stylus 3 and outputs a detection signal. Asensing pin 6 as a contact portion is adhered and fixed on a tip end ofthe stylus 3, the sensing pin 6 made from diamond-tip, ruby or the like.The oscillation element 4 and the detection element 5 constitute ameasuring force detecting unit that detects a measuring force when thesensing pin 6 of the stylus 3 contacts the surface of the workpiece. Theoscillation element 4 and the detection element 5 are each formed by apiezoelectric element. One oscillation element 4 and one detectionelement 5 are adhered and fixed on a front surface of the base 2 and ona rear surface of the base 2.

As shown in FIG. 11, when an oscillation signal Pi (a voltage signal)having a specific frequency and amplitude is given to the oscillationelement 4 of the force sensor 1, the detection element 5 obtains adetection signal Qo (a voltage signal) having a specific frequency andamplitude.

FIG. 12 shows change in amplitude of the detection signal Qo whichaccompanies a contact with the workpiece. When the oscillation signal Pihaving a certain oscillation at a resonance frequency of the stylus 3 isadded to the oscillation element 4 in a state where the stylus 3 is notin contact with the workpiece, the stylus 3 resonates and the detectionelement 5 can obtain the detection signal Qo having an amplitude Ao.When the stylus 3 contacts the workpiece W, the amplitude of thedetection signal Qo is attenuated from Ao to Ax.

The attenuation ratio k (Ax/Ao) and the measuring force have arelationship shown in FIG. 13.

Herein, taken as an example is a case in which the detection signal Qogenerated when the stylus 3 (the force sensor 1) contacts the workpieceW is attenuated to 90% of that generated when the stylus 3 is not incontact with the workpiece W (the attenuation ratio k=0.9). From therelationship shown in FIG. 13, the measuring force in the non-contactingstate is 135 [μN].

Accordingly, when the force sensor 1 is brought into contact with theworkpiece W, it is possible to measure the profile and the roughness ofthe workpiece W with the constant measuring force by controlling adistance between the force sensor 1 and the workpiece W using theactuator or the like such that the attenuation ratio k is alwaysconstant.

<Texture Measuring System Using Force Sensor>

FIG. 14 shows an example of a texture measuring system using the forcesensor 1. The texture measuring system includes a probe 10 and acontroller 20 that controls the probe 10.

The probe 10 includes the force sensor 1, an actuator 11 that advancesand retracts the force sensor 1 relative to the workpiece W and adetector (having a scale and a detection head) 12 that detects adisplacement amount by which the force sensor 1 is displaced by theactuator 11 (measuring point information on the workpiece W whenmeasured by the force sensor 1).

The controller 20 includes an oscillator 21 that gives the oscillationsignal to the force sensor 1 in order to oscillate the force sensor 1, apeak hold circuit 22 that converts the detection signal from the forcesensor 1 into a direct-current signal, an processing unit 23 thatcomputes a deviation between an output from the peak hold circuit 22 (aforce sensor signal) and a target measuring force, a force controlcompensator 24 that is input with an output from the processing unit 23,a drive amplifier 25 that drives the actuator 11 based on an output fromthe force control compensator 24 and a counter 26 that counts a signalfrom the detector 12 and outputs the measuring point information of theforce sensor 1 as a position measurement value.

In FIG. 14, when the stylus 3 of the force sensor 1 is brought intocontact with the workpiece W, the detection signal at that time isoutput from the force sensor 1. The detection signal is converted into adirect-current signal by the peak hold circuit 22 and then given to theprocessing unit 23. The processing unit 23 calculates the deviationbetween the detection signal from the peak hold circuit 22 (the forcesensor signal) and the target measuring force. The deviation ismultiplied by a gain of the force control compensator 24 and the resultis given to the drive amplifier 25, so that the actuator 11 drives suchthat the deviation is eliminated.

<Method for Using Force Sensor as Probe>

FIG. 15 shows changes in the detection signal from the force sensor 1(the force sensor signal) which is generated when the force sensor 1moves from the non-contacting state to a contacting state.

When the force sensor 1 is brought into contact with the workpiece W andfurther pressed to the workpiece W, the detection signal from the forcesensor 1 (the force sensor signal) gradually drops and becomessubstantially coincident with the target measuring force to be stable inthis state. In the state, when the force sensor 1 and the workpiece arerelatively moved along the surface profile of the workpiece, since thedetection signal from the force sensor 1 and the target measuring forceare maintained to be substantially coincident with each other, theprofile or the roughness of the workpiece can be scanning-measured withthe constant measuring force by collecting the position measurementvalue from the detector 12.

<Method for Using Force Sensor as Touch Probe>

In the texture measuring system of FIG. 14, when the attenuation ratiobecomes a desired value, the force sensor 1 can be used as a touch probewith the constant measuring force by incorporating a circuit thatlatches a current position.

As shown in FIG. 16, by comparing the force sensor signal representingthe detection signal oscillation of the force sensor 1 with a contactdetection level (a threshold value) for detecting a contact with theworkpiece, it is possible to structure a circuit that outputs a touchsignal representing a contact between the force sensor 1 and theworkpiece. In this arrangement, the touch signal is generated when theforce sensor signal passes the contact detection level (the thresholdvalue), so that the same measuring force is always generated at thetiming of the touch signal generation (thereby realizing higherprecision).

As shown in FIG. 17, the measuring force can be also controlled bycontrolling the contact detection level (the threshold value) and ameasurement with a lower measuring force can be enabled by raising thecontact detection level, thereby realizing a ultra-precise measurement.

<Probe with Constant Force Scanning Measurement Function and TouchMeasurement Function>

As understood from the above description, when the probe is used as ascanning probe or a touch probe, the force sensor can be used in acommon way (under the same detection principle).

Note that there has been suggested a system that includes both functionsof a scanning measurement and a touch measurement, drives a probemounting portion by a coordinate drive mechanism that provides athree-dimensional drive and switches between the constant force scanningmeasurement and the touch measurement depending on the workpiece(Document: JP-A-2005-254016, for reference).

However, it is sometimes difficult to conduct a constant force scanningcontrol due to the surface profile, the surface texture and propertyfluctuation owing to material of the workpiece or disturbance input tothe system. When the constant force scanning control is difficult,namely when the force control is unstable, the scanning control may beoscillatory to cause variation in the measurement value, so that thehigh precision cannot be maintained. As a compensatory function, aswitching is conducted between the constant force scanning measurementand the touch measurement.

For example, in a case shown in FIG. 18, when the scanning controlbecomes oscillatory during the scanning measurement, it becomesimpossible to maintain the high precision due to variation in themeasurement value, so that an operator judges the situation to manuallyswitch from the scanning measurement mode to the touch measurement mode.Alternatively, when the oscillation range of the force sensor signalexceeds a preset predetermined value, a switching is conducted from thescanning measurement mode to the touch measurement mode. Further, byassuming in advance the surface profile of the workpiece, a switchingfrom the scanning measurement mode to the touch measurement mode isautomatically conducted upon an entry into a touch measurement region.Accordingly, the force sensor contacts the workpiece surface whilerepeating touch-back operations (i.e. operations in which the forcesensor is moved away from the workpiece surface and brought into contactwith the surface again) along the surface, so that the touch signal iscollected at the timing of the touch signal generation.

However, in order to compensate the profile scanning measurement by thenormal touch measurement, it is necessary to conduct the touchmeasurement at a shorter pitch than a workpiece profile cycle, whichrequires a longer measurement time.

Generally, the constant force scanning measurement is more advantageousthan the touch measurement for measuring a fine profile, since adistance between data-measured points is smaller in the constant forcescanning measurement than in the touch measurement, so that a fineprofile cycle can be measured. Therefore, there have been demands forthe use of the constant force scanning measurement as far as possible.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a surface texturemeasuring instrument that can ensure high precision even under thepresence of property fluctuation caused by a surface texture of aworkpiece or disturbance and can ensure a scanning measurement with aconstant measuring force while avoiding an increase in measurement time.

A surface texture measuring instrument according to an aspect of theinvention includes: a measuring portion including a stylus having acontact portion that contacts a surface of a workpiece and a measuringforce detecting unit that detects a measuring force when the contactportion contacts the surface of the workpiece; a relative movement unitthat relatively moves the measuring portion and the workpiece; aposition detecting unit that outputs as measuring point information ameasuring point on which the workpiece is measured by the measuringportion, the measuring point information from the position detectingunit being collected while the relative movement unit is driven with thecontact portion of the stylus contacting with the surface of theworkpiece, a surface texture of the workpiece being measured from themeasuring point information, a scanning controller that collects adetection measuring force from the measuring portion and drives therelative movement unit such that the detection measuring forcesubstantially coincides with a target measuring force; a touch signalgenerating unit that collects the detection measuring force from themeasuring portion and generates a touch signal when the detectionmeasuring force coincides with a contact measuring force; and ameasurement value collecting unit that collects the measuring pointinformation from the position detecting unit based on a predeterminedcondition when a fluctuation range of the detection measuring force fromthe measuring potion is within a preset certain range, the measurementvalue collecting unit collecting the measuring point information fromthe position detecting unit each time the touch signal is generated fromthe touch signal generating unit when the detection measuring force fromthe measuring portion oscillates and an oscillation range exceeds apreset certain range, when the scanning controller is in operation.

According to the aspect of the invention, the detection measuring forcefrom the measuring portion is collected by the scanning controller, andthe scanning controller drives the relative movement unit such that thedetection measuring force substantially coincides with the targetmeasuring force. Accordingly, the surface texture of the workpiece isscanning-measured in a state in which the stylus of the measuringportion is in contact with the workpiece and the detection measuringforce is controlled so as to be substantially coincident with the targetmeasuring force.

Herein, when the fluctuation range of the detection measuring force fromthe measuring portion is within the preset certain range, the measuringpoint information from the position detecting unit is collected based onthe predetermined condition. Hence, in this state, the measurement canbe conducted in the normal scanning measurement. Note that thepredetermined condition is a predetermined time interval or apredetermined positional interval.

On the other hand, in the scanning measurement, when the detectionmeasuring force from the measuring portion oscillates and theoscillation exceeds the preset certain range, namely when the detectionmeasuring force from the measuring portion becomes oscillatory due tospecific fluctuation caused by the profile, material, surface textureand the like of the workpiece or disturbance, the measuring forcefluctuates, causing variation in the measuring value.

In this state, the measuring point information from the positiondetecting unit is collected each time the touch signal is generated bythe touch signal generating unit. Since the touch signal is generatedwhen the detection measuring force coincides with the contact measuringforce, it is possible to collect the measurement value with the constantmeasuring force. In addition, since the measurement accompanies noswitching from the scanning measurement to the touch measurement, timeloss in touch-back operations can be eliminated.

Hence, even under the presence of the property fluctuation caused by thesurface texture of the workpiece and the like or the disturbance, thescanning measurement can be conducted with the constant measuring forcewhile ensuring high precision and avoiding an increase in themeasurement time.

A surface texture measuring instrument according to an aspect of theinvention, includes: a measuring portion including a stylus having acontact portion that contacts a surface of a workpiece and a measuringforce detecting unit that detects a measuring force when the contactportion contacts the surface of the workpiece; a relative movement unitthat relatively moves the measuring portion and the workpiece; aposition detecting unit that outputs as measuring point information ameasuring point on which the workpiece is measured by the measuringportion, the measuring point information from the position detectingunit being collected while the relative movement unit is driven with thecontact portion of the stylus contacting the surface of the workpiece, asurface texture of the workpiece being measured from the measuring pointinformation, a scanning controller that collects a detection measuringforce from the measuring portion and drives the relative movement unitsuch that the detection measuring force substantially coincides with atarget measuring force; a touch signal generating unit that collects thedetection measuring force from the measuring portion and generates atouch signal when the detection measuring force coincides with a contactmeasuring force; a switch unit that switches a scanning measurement modeand a touch measurement mode; and a measurement value collecting unitthat collects the measuring point information from the positiondetecting unit based on a predetermined condition when the switch unitis switched to the scanning measurement mode, the measurement valuecollecting unit collecting the measuring point information from theposition detecting unit each time the touch signal is generated from thetouch signal generating unit in a state where the switch unit is in thetouch measurement mode, when the scanning controller is in operation.

According to the aspect of the invention, since the switch unit thatswitches the scanning measurement mode and the touch measurement isprovided, the measurement mode can be switched from the scanningmeasurement mode to the touch measurement mode by a switching operationwith the switch unit. Accordingly, since the measuring point informationfrom the position detecting unit is collected each time the touch signalis generated by the touch signal generating unit, the advantages similarto those described above can be expected. Note that the predeterminedcondition is the predetermined time interval or the predeterminedpositional interval.

In the surface texture measuring instrument according to the aspect ofthe invention, the switch unit may include a switch portion thatswitches between the scanning measurement mode and the touch measurementmode in accordance with a surface profile of the workpiece based on aselection made by a user.

According to the aspect of the invention, the user monitors aninclination or curvature of the workpiece surface and selects which partof the workpiece surface is to be scanning-measured or touch-measured.Since the user can arbitrarily select the measuring mode by theswitching portion, the measurement mode can be selected more speedilyand appropriately as compared with, for example, a case in which theinstrument automatically selects the most appropriate measurement modeby repeating the scan-measurement and the touch measurement in atrial-and-error manner. Thus, an effective measurement can be realized.

In the surface texture measuring instrument according to the aspect ofthe invention, the switch unit may include a switch portion thatswitches between the scanning measurement mode and the touch measurementmode and a switching controller that controls the switch portion, andthe switching controller switches the switch portion based on a changein the detection measuring force detected by the measuring forcedetecting unit.

In the scanning measurement, the detection measuring force from themeasuring portion may be oscillatory depending on the surface profile orthe material of the workpiece or a relative angle between a detectingdirection and a normal line of the workpiece surface. In this state, themeasuring force fluctuates, so that the measurement cannot be conductedwith the constant measuring force.

According to the aspect of the invention, since the measurement mode isswitched to the touch measurement based on a change in the measuringforce detected by the measuring force detecting unit (for example, whenthe detection measuring force from the measuring portion oscillates andthe oscillation range exceeds the preset certain range), the measuringmode can be selected more speedily and appropriately as compared withthe arrangement in which the user manually selects the most appropriatemeasurement mode in a trial-and-error manner by arbitrarily switchingthe switching portion. Thus, an effective measurement can be realized

In the surface texture measuring instrument according to the aspect ofthe invention, the switch unit may include a switch portion thatswitches between the scanning measurement mode and the touch measurementmode and a switching controller that controls the switch portion, andthe switching controller may switch the switch portion based on thesurface profile of the workpiece.

Herein, to switch the switching portion based on the surface profile ofthe workpiece conducted by the switching controller means, for example,a switching in which the surface profile of the workpiece is calculatedbased on data from an already-conducted measurement and the scanningmeasurement or the touch measurement is selected based on the curvatureof the workpiece surface or an angle formed between the workpiecesurface and the measuring force detecting direction. Alternatively, theprofile of the workpiece surface is obtained from design data of theworkpiece and the curvature or the inclination of the workpiece surfacemay be obtained from the design data.

According to the aspect of the invention, the surface profile of theworkpiece is analyzed and a switching control to switch to the touchmeasurement is conducted based on the curvature, the inclination or thelike, so that the user does not need to judge and switch, therebysimplifying the measurement. Even when the workpiece has a surfaceprofile that cannot be measured in the scanning measurement, the profilemeasurement can be automatically conducted in the touch measurement.

In the surface texture measuring instrument according to the aspect ofthe invention, the scanning controller may include a processing unitthat computes a deviation between the detection measuring force from themeasuring portion and the target measuring force and outputs thedeviation; and a gain adjusting unit that amplifies an output signalfrom the processing unit and gives the output signal to the relativemovement unit, and a setting gain of the gain adjusting unit may beadjustable such that the detection measuring force from the measuringportion oscillates.

According to the aspect of the invention, an oscillating state of thedetection measuring force from the measuring portion can be obtained byadjusting the setting gain of the gain adjusting unit, so that relativemovement position data from the position detecting unit can be acquiredcyclically at rapid timing. Hence, the precision can be more enhanced.

In the surface texture measuring instrument according to the aspect ofthe invention, the relative movement unit may include a fine feedingmechanism that finely displaces the measuring portion and a coarsefeeding mechanism that displaces the measuring portion in cooperationwith the fine feeding mechanism by a larger amount than the fine feedingmechanism, the scanning controller includes the processing unit thatcomputes the deviation between the detection measuring force from themeasuring portion and the target measuring force and outputs thedeviation; and the gain adjusting unit that amplifies an output signalfrom the processing unit and gives the output signal to the fine feedingmechanism, and the setting gain of the gain adjusting unit may beadjustable such that the detection measuring force from the measuringportion oscillates.

Herein, the fine feeding mechanism may be a drive mechanism that hashigh response speed. For example, the fine feeding mechanism may be apiezoelectric actuator using a piezoelectric element. The coarse feedmechanism may be an electromagnetic actuator.

According to the aspect of the invention, since the fine feedingmechanism and the coarse feed mechanism are provided, in the scanningmeasurement, it is possible to speedily and finely displace the contactportion in response to fine unevenness of the workpiece surface by thefine feeding mechanism that has the high response speed, while it ispossible to respond to large profile change (undulation and the like) ofthe workpiece surface by the coarse feed mechanism capable of respondingto a large displacement. As a result, the contact portion can beprecisely and speedily moved in a scanning manner along the workpiecesurface.

A surface texture measuring instrument according to an aspect of theinvention includes: a measuring portion including a stylus having acontact portion that contacts a surface of a workpiece and a measuringforce detecting unit that detects a measuring force when the contactportion contacts the surface of the workpiece; a relative movement unitthat relatively moves the measuring portion and the workpiece; aposition detecting unit that outputs as measuring point information ameasuring point on which the workpiece is measured by the measuringportion, a force control loop that collects a measuring force detectedby the measuring portion and drives the relative movement unit such thatthe detection measuring force substantially coincides with a targetmeasuring force; a touch signal generating unit that collects thedetection measuring force detected by the measuring portion andgenerates a touch signal when the detection measuring force coincideswith a contact measuring force; and a measurement value collecting unitthat collects the measuring point information from the positiondetecting unit each time the touch signal is generated from the touchsignal generating unit. The force control loop is adjustable such thatthe detection measuring force detected by the measuring force detectingunit oscillates.

According to the aspect of the invention, the force control loop is setsuch that the detection measuring force detected by the measuring forcedetecting unit oscillates with the contact portion of the stylus incontact with the workpiece surface. The measurement is conducted in thisstate. Accordingly, the touch signal is generated each time thedetection measuring force coincides with the target measuring force andthe measuring point information from the position detecting unit iscollected by the measurement value collecting unit each time the touchsignal is generated.

In other words, since the touch signal is generated utilizing theoscillating state of the detection measuring force, a high-speed touchsignal can be generated and the measuring point information can becollected at the timing of the generation of such a touch signal,thereby realizing a precise measurement. Particularly, since themeasurement is conducted utilizing the unstable oscillation of the forcecontrol loop, it is possible to stably trace the profile with toleranceto the disturbance. Thus, it is possible to measure the workpieceincluding a steeply inclined surface, thereby increasing scanning speed.

Hence, even under the presence of the specific fluctuation caused by thesurface texture of the workpiece and the like and the disturbance, thescanning measurement can be conducted with the constant measuring forcewhile ensuring high precision and avoiding an increase in themeasurement time.

In the surface texture measuring instrument according to the aspect ofthe invention, the force control loop may include a processing unit thatcomputes a deviation between the detection measuring force detected bythe measuring force detecting unit and the target measuring force andoutputs the deviation; and a gain adjusting unit that amplifies anoutput from the processing unit by a setting gain and gives the outputto the relative movement unit, and the setting gain of the gainadjusting unit of the force control loop may be adjustable such that thedetection measuring force detected by the measuring force detecting unitoscillates.

According to the aspect of the invention, the oscillating state of thedetection measuring force from the measuring portion can be obtained byadjusting the setting gain of the gain adjusting unit, so that relativemovement position data from the position detecting unit can becyclically acquired at rapider timing. Hence, the precision can be moreenhanced.

In the surface texture measuring instrument according to the aspect ofthe invention, the relative movement unit may include a fine feedingmechanism that finely displaces the measuring portion and a coarse feedmechanism that displaces the measuring portion in cooperation with thefine feeding mechanism by a larger amount than the fine feedingmechanism. The force control loop may include a processing unit thatcomputes a deviation between the detection measuring force detected bythe measuring force detecting unit and the target measuring force andoutputs the deviation; and a gain adjusting unit that amplifies anoutput from the processing unit by a setting gain and gives the outputto the fine feeding mechanism. The setting gain of the gain adjustingunit of the force control loop may be adjustable such that the detectionmeasuring force detected by the measuring portion oscillates.

According to the aspect of the invention, since the fine feedingmechanism and the coarse feed mechanism are provided, in the scanningmeasurement, it is possible to speedily and finely displace the contactportion in response to fine unevenness of the workpiece surface by thefine feeding mechanism that has the high response speed, while it ispossible to respond to large profile change (undulation and the like) ofthe workpiece surface by the coarse feed mechanism capable of respondingto a large displacement. As a result, the contact portion can be movedin a scanning manner along the workpiece surface precisely and speedily.

In the surface texture measuring instrument according to the aspect ofthe invention, the touch signal generating unit may generate a touchsignal when the detection measuring force from the measuring portionpasses the contact measuring force from a value higher than the contactmeasuring force and when the detection measuring force from themeasuring portion passes the contact measuring force from a value lowerthan the contact measuring force.

According to the aspect of the invention, the touch signal is generatedwhen the detection measuring force from the measuring portion passes thecontact measuring force from a value higher than the contact measuringforce and when the detection measuring force from the measuring portionpasses the contact measuring force from a value lower than the contactmeasuring force, so that the measuring point information from theposition detecting unit can be acquired cyclically at a rapid timing.Hence, the precision can be more enhanced.

In the surface texture measuring instrument according to the aspect ofthe invention, the measuring portion may include: an oscillation elementthat oscillates the stylus; and a detection element that detects anoscillation of the stylus (3) to be output as a detection signal.

According to the aspect of the invention, when the contact portioncontacts the workpiece surface and the oscillation of the stylus issuppressed, the oscillation level becomes small. From the difference inthe oscillation, the measuring force that is applied on the contactportion from the workpiece surface can be detected. In particular, sincethe measuring force is detected from the attenuation of the oscillationcaused by suppressing the oscillation, so that the measuring force canbe precisely detected even when the measuring force is low.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a first embodiment of a surfacetexture measuring instrument according to the invention;

FIG. 2 is a diagram for showing a touch signal when a force sensorsignal oscillates in the first embodiment;

FIG. 3 is a diagram for showing the touch signal when the force sensorsignal oscillates in the first embodiment;

FIG. 4 is a block diagram showing a second embodiment of the surfacetexture measuring instrument according to the invention;

FIG. 5 is a block diagram showing a modification of the secondembodiment;

FIG. 6 is a block diagram showing a third embodiment of the surfacetexture measuring instrument according to the invention;

FIG. 7 is a block diagram showing a fourth embodiment of the surfacetexture measuring instrument according to the invention;

FIG. 8 is a block diagram showing a modification of the fourthembodiment;

FIG. 9 is a perspective view showing a modification of a measuringportion;

FIG. 10 is an exploded perspective view showing an arrangement of aforce sensor;

FIG. 11 is an illustration showing an oscillation signal and a detectionsignal which are given to the force sensor;

FIG. 12 is a diagram showing change in the detection signal when theforce sensor contacts a workpiece;

FIG. 13 is a graph showing a relationship between an attenuation ratioof the detection signal of the force sensor and a measuring force;

FIG. 14 is a block diagram showing a texture measuring system using theforce sensor;

FIG. 15 is a diagram showing changes in the force sensor signal in thesystem of FIG. 14;

FIG. 16 is a diagram showing a relationship among the force sensorsignal, a contact detection level and the touch signal in the system ofFIG. 14;

FIG. 17 is a diagram showing a result from fluctuating the contactdetection level up and down in the system of FIG. 14; and

FIG. 18 is a diagram showing a result when the force sensor signaloscillates in a system having a scanning measurement mode a touchmeasurement mode.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S) First Embodiment<Description of Overall Arrangement of First Embodiment (FIG. 1)>

FIG. 1 is a block diagram showing a first embodiment of a surfacetexture measuring instrument according to the invention. The samecomponents between FIG. 1 and FIG. 14 are given the same referencenumerals and explanation for the components will be omitted orsimplified in the description of FIG. 1.

The surface texture measuring instrument of the first embodimentincludes a probe 10, a coordinate drive mechanism 40 and a controller 50that controls the probe 10.

Similarly to FIG. 14, the probe 10 includes: a force sensor 1; anactuator 11 as a relative movement unit that moves (advances andretracts) the force sensor 1 relative to a workpiece W; and a detector12 as a position detecting unit that detects a displacement amount inwhich the force sensor 1 is moved by the actuator 11 (namely, measuringpoint information on a measuring point of the workpiece W when measuredby the force sensor 1), the detector 12 including a scale and adetecting head.

The coordinate drive mechanism 40 and the actuator 11 constitute therelative movement unit. The coordinate drive mechanism 40 drives a mountportion of the probe 10 in three dimensional directions (the X-, Y- andZ-axis directions). Note that the coordinate drive mechanism 40 is notlimited to an arrangement in which the probe 10 is driven in the threedimensional directions. The coordinate drive mechanism 40 may drive theworkpiece W in at least the three dimensional directions or may driveone of the probe 10 and the workpiece W in one axis direction and theother in the other axis directions.

The controller 50 includes an oscillator 21, a peak hold circuit 22 andthe counter 26 similarly to FIG. 14, the controller 50 further includinga touch signal generator 51, a latch counter 52 and a scanningmeasurement controller 53.

The touch signal generator 51 (a touch signal generating unit) collectsa detection signal from the force sensor 1 (a force sensor signal as adetection measuring force) via the peak hold circuit 22. When thedetection signal coincides with a contact measuring force as a settingvalue (a contact detection level), herein when the detection signalpasses the contact measuring force (the contact detection level) from avalue higher than the contact measuring force, the touch signalgenerator 51 generates a touch signal and gives the touch signal to thelatch counter 52.

The latch counter 52 latches a count value of the counter 26 each timethe touch signal is given by the touch signal generator 51 and gives thecount value to the scanning measurement controller 53 (a later-describedmeasurement value collecting unit 55).

The scanning measurement controller 53 includes a scanning controller 54and the measurement value collecting unit 55.

The scanning controller 54 collects the detection signal from the forcesensor 1 via the peak hold circuit 22, the scanning controller 54driving the actuator 11 such that the detection signal substantiallycoincides with a target measuring force that is the setting value.Although not shown, similarly to FIG. 14, the scanning controller 54includes a processing unit 23 that computes a deviation between anoutput from the peak hold circuit 22 (the force sensor signal) and thetarget measuring force, a force control compensator 24 to which anoutput from the processing unit 23 is input and a drive amplifier 25that drives the actuator 11 based on the output from the force controlcompensator 24.

When the scanning controller 54 is in operation, the measurement valuecollecting unit 55 collects the detection signal from the force sensor 1(the force sensor signal) via the peak hold circuit 22 and judgeswhether or not a fluctuation range of the detection signal is within apreset certain range (whether or not the fluctuation range is a range ofwhich variation in a measurement value is ignorable). When thefluctuation range of the detection signal is within the preset certainrange, the measurement value collecting unit 55 collects a positionmeasurement value (the measuring point information) at a predeterminedtime interval. When the detection signal from the force sensor 1oscillates and its oscillation range exceeds the preset certain range,the measurement value collecting unit 55 collects the positionmeasurement value (the measuring point information) which the latchcounter 52 latches each time the touch signal is generated from thetouch signal generator 51.

<Scanning Measurement with Constant Force>

The detection signal from the force sensor 1 (the force sensor signal)is collected by the scanning controller 54 and the scanning controller54 drives the actuator 11 such that the detection signal substantiallycoincides with the target measuring force (a reference value).Accordingly, a stylus 3 of the force sensor 1 contacts the workpiece,and a surface texture of the workpiece is scanning-measured with themeasuring force maintained to the target measuring force.

When a constant force control is stably controlled (for example, asshown in FIG. 14), deformation amounts of the force sensor 1 and theworkpiece are constant, so that a measurement can be conducted with thevariation in the measurement value suppressed.

However, when it becomes difficult to conduct a constant force scanningcontrol due to property fluctuation caused by the surface profile,surface texture or material of the workpiece or disturbance input to thesystem, the deformation amounts of the force sensor 1 and the workpiecechange in accordance with the unstable measuring force. Hence, thevariation in the measuring value becomes large.

For example, as shown in FIG. 2, the variation in the measuring forcebecomes large when the detection signal from the force sensor 1 (theforce sensor signal) reaches the target measuring force and thenoscillates.

Herein, each time the detection signal passes the target measuring forcefrom a value higher than the target measuring force, the touch signalgenerator 51 generates the touch signal. The touch signal is given tothe latch counter 52, so that the count value of the counter 26 islatched by the latch counter 52.

At the same time, the detection signal from the sensor 1 is also givento the measurement value collecting unit 55. The measurement valuecollecting unit 55 judges whether or not the fluctuation range of thedetection signal from the force sensor 1 is within the preset certainrange. When the fluctuation range of the detection signal is within thepreset certain range, the measurement value collecting unit 55 collectsthe position measurement value from the counter 26 at a predeterminedtime interval. When the detection signal from the force sensor 1oscillates and its oscillation range exceeds the preset certain range,the measurement value collecting unit 55 collects a value of the latchcounter 52, namely the position measurement value that the latch counter52 latches each time the touch signal is generated from the touch signalgenerator 51.

Since scanning controller 54 is in operation even when the detectionsignal from the force sensor 1 oscillates, an average value of theoscillation of the detection signal from the force sensor 1 iscontrolled to substantially coincide with the target measurement value.

Since the touch signal is generated when the detection signal coincideswith the contact measuring force, it is possible to collect themeasurement value with the constant measuring force. In other words, themeasurement value is a value obtained when the measuring force isconstant, so that it is possible to obtain the measurement valueequivalent to that in the constant force control. As a result, it ispossible to suppress the variation in the measurement value.

Further, since the touch signal is generated during tracing the profileof the workpiece (during the scanning control), a touch-back operationof a related-art touch probe is not required, thereby shorteningmeasurement time. In short, time loss accompanying the touch-backoperation can be eliminated.

Accordingly, even in the presence of the specific fluctuation caused bythe surface texture of the workpiece and the like and the disturbance,the scanning measurement can be conducted with the constant measuringforce while ensuring high precision and avoiding an increase in themeasurement time.

The above-described way contains a drawback that the touch signal cannotbe generated at an arbitrarily selected regular cycle. Hence, thefollowing methods can be suggested to compensate for the drawback.

<(1) Method for Shortening Touch Signal Generation Cycle by ChangingTouch Signal Generation Condition>

Although a method explained in FIG. 2 employs a circuit that generatesthe touch signal only when the detection signal of the force sensor 1passes the contact detection level from a higher value to a lower valueof the level, herein the touch signal is generated at both time pointswhen the detection signal passes from a higher value to a lower valueand from a lower value to a higher value as shown in FIG. 3. In short,the touch signal generator 51 of FIG. 1 is provided to a circuit thatgenerates the touch signal at both of the time points. This arrangementcan shorten the touch signal generation cycle, thereby enhancing theprecision. (FIGS. 2 and 3 show a case where the target measuring forceof the scanning controller 54 and the contact measuring force of thetouch signal generator 51 have the same value.)

Note that the above-described method can be used together with anext-described method (2) for high frequency oscillation by increasing again of the force control loop.

<(2) Method for High Frequency Oscillation by Increasing Gain of ForceControl Loop>

There are two reasons for unstable constant force scanning control.

(a) The force is disturbed by the disturbance that the force controlcannot suppress.(b) High gain of the force control loop causes unstable high frequencyrange, triggering an oscillating state.

The state in (b) is undesirable in a normal control. However, in thepresent method, it is possible to acquire the measurement value withsmaller variation even in the above-stated oscillating state. When theoscillation is caused by the high gain of the force control loop, theoscillation is often at a resonance frequency in the high frequencyrange of a mechanical system of the probe. Hence, by utilizing thisoscillation phenomenon, continuous touching in a high cycle can berealized.

Specifically, similarly to FIG. 14, the scanning controller 54 includes:the processing unit 23 that computes the deviation between the detectionsignal from the force sensor 1 and the target measuring force andoutputs the computed deviation; the force control compensator 24 as thegain adjusting unit that amplifies the output signal from the processingunit 23 by a setting gain and outputs the amplified signal; and thedrive amplifier 25 that drives the actuator 11 as the relative movementunit based on the output from the force control compensator 24. Thus, anoperator manually adjusts or switches the gain of the force controlcompensator 24 to high when a scanning point of the force sensor 1 andthe workpiece enters a region in which the detection signal from theforce sensor 1 oscillates, for example.

Alternatively, a circuit that detects that the detect signal from theforce sensor 1 is oscillatory and that the oscillation range exceeds thepreset certain range may be provided and, by the use of the circuit, thegain of the force control compensator 24 is adjusted or switched tohigh.

With such an arrangement, an oscillating state of the detection signalfrom the force sensor 1 can be obtained, so that the positionmeasurement value from the detector 12 can be obtained cyclically atrapid timing. Hence, the precision can be more enhanced.

Second Embodiment <Description of Second Embodiment (FIG. 4)>

In the first embodiment, the value of the latch counter 52 is collectedat the timing of the generation of the touch signal on condition thatthe detection signal from the force sensor 1 exceeds the preset certainrange. In the second embodiment, as shown in FIG. 4, a switch unit 56that switches the scanning measurement mode and the touch measurementmode is provided.

The switch unit 56 includes a switching portion 56A that switches thescanning measurement mode and the touch measurement mode in accordancewith the surface profile of the workpiece based on a selection by auser. In short, the switching portion 56A is inserted on a measurementvalue collecting unit 55 side to enable a switching between terminals ofthe counter 26 and the latch counter 52.

When the scanning controller 54 is in operation and the switchingportion 56A of the switch unit 56 is switched to one side (a counter 26side), the measurement value collecting unit 55 collects the positionmeasurement value (the measuring point information) from the counter 26as the position detecting unit at a predetermined time interval. Whenthe switching portion 56A is switched to the other side (a latch counter52 side), the measurement value collecting unit 55 collects the countvalue of the latch counter 52, namely the count value that is latched bythe latch counter 52 each time the touch signal is generated from thetouch signal generator 51.

In such an arrangement, the user judges the surface profile of theworkpiece and switches the switching portion 56A of the switch unit 56to the other side (the latch counter 52 side) when the scanning positionof the force sensor 1 and the workpiece enters a region in which thedetection signal from the force sensor 1 may be oscillatory. Then, themeasuring value of the counter 26 is latched by the latch counter 52each time the touch signal is generated from the touch signal generator51 and the measurement value is collected by the measurement valuecollecting unit 55, thereby providing advantages similar to thosedescribed above.

Hence, according to the second embodiment, the user monitors aninclination or a curvature of the surface of the workpiece and selectswhich part of the surface of the workpiece is to be scanning-measured ortouch-measured. Since the user can arbitrarily select the measuring modeby switching the switching portion, the measurement mode can be selectedmore speedily and appropriately as compared with, for example, a case inwhich the instrument automatically selects the most appropriatemeasurement mode by repeating the scan-measurement and the touchmeasurement in a trial-and-error manner, thereby realizing an effectivemeasurement.

<Description of Modification of Second Embodiment (FIG. 5)>

In the second embodiment, the switching portion 56A of the switch unit56 may be automatically switched instead of being manually switched bythe user.

For example, in a modification shown in FIG. 5, the switch unit 56includes the switching portion 56A that switches the scanningmeasurement mode and the touch measurement mode and a switchingcontroller 56B that controls the switching portion 56A. The switchingcontroller 56B switches the switching portion 56A based on changes inthe force sensor signal detected by the force sensor 1 as the measuringforce detecting unit.

In the scanning measurement, the force sensor signal from the forcesensor 1 may be oscillatory depending on the surface profile or thematerial of the workpiece. In this state, the measuring forcefluctuates, so that the measurement cannot be conducted with theconstant measuring force. In an example shown in FIG. 5, since theswitching controller 56B switches the switching portion 56A to the latchcounter 52 side based on the changes in the force sensor signal detectedby the force sensor 1 (for example, when the force sensor signaloscillates and the oscillation range exceeds the preset certain range),the measurement mode can be selected more speedily and appropriately ascompared with the case in which the user manually selects the mostappropriate measurement mode in a trial-and-error manner by arbitrarilyswitching the switching portion, thereby realizing an effectivemeasurement

The switch unit 56 may be constituted by the switching portion 56A thatswitches between the scanning measurement mode and the touch measurementmode and the switching controller 56B that controls the switchingportion 56A. The switching controller 56B may be adapted to switch theswitching portion 56A based on the surface profile of the workpiece.

For example, the surface profile of the workpiece is calculated based onmeasurement data of already-conducted measurements, and the scanningmeasurement and the touch measurement may be switched based on thecalculated curvature of the workpiece surface or a calculated angleformed between the workpiece surface and a measuring force detectingdirection. Alternatively, the profile of the workpiece surface isobtained from design data of the workpiece and the curvature or theinclination of the workpiece surface is obtained from the design data.Then, the scanning measurement and the touch measurement may be switchedbased on the curvature or the inclination.

With such an arrangement, the surface profile of the workpiece can beanalyzed and a switching control to switch to the touch measurement canbe conducted based on the curvature or the inclination, so that the userdoes not need to judge and switch, thereby simplifying the measurement.Even when the workpiece has a surface profile that cannot be measured inthe scanning measurement, the profile measurement can be automaticallyconducted in the touch measurement.

Third Embodiment <Description of Third Embodiment (FIG. 6)>

The first embodiment employs the arrangement in which a constantscanning force control is firstly conducted with an appropriately-setgain of the force control compensator 24 of the scanning controller 54.In the arrangement, the gain of the force control compensator 24 isadjusted or switched to high by the user when, for example, the scanningpoint of the force sensor 1 and the workpiece enters the region in whichthe detection signal from the force sensor 1 oscillates or it isadjusted or switched with the circuit provided for detecting that thedetection signal from the force sensor 1 is oscillatory and that theoscillation range exceeds the preset certain range.

As shown in FIG. 6, the controller 50 in the third embodiment includes:a force control loop 28 that collects the force sensor signal (thedetection measuring force) detected by the force sensor 1 as themeasuring portion and drives the actuator 11 (the relative movementunit) such that the force sensor signal coincides with the targetmeasuring force; the touch signal generator 51 that collects the forcesensor signal detected by the force sensor 1 and generates the touchsignal when the force sensor signal coincides with the contact measuringforce; and the measurement value collecting unit 55 that collects themeasuring point information from the counter 26 each time the touchsignal is generated from the touch signal generator 51. The controller50 is arranged such that the scanning measurement can be conducted bypresetting the force control loop 28 to an unstable state.

Similarly to the scanning controller 54 of FIG. 1 and the force controlloop of FIG. 14, the force control loop 28 includes the processing unit23 that outputs the deviation between the force sensor signal detectedby the force sensor 1 (the measuring force detecting unit) and thetarget measuring force; the force control compensator 24 as the gainadjusting unit that amplifies the output from the processing unit 23 bythe setting gain to output; and the drive amplifier 25 that amplifiesthe output from the force control compensator 24 to give the amplifiedoutput the actuator 11.

The force control loop 28 can be set such that the force sensor signaldetected by the force sensor 1 oscillates. In other words, the settinggain of the force control compensator 24 of the force control loop 28can be set such that the force sensor signal oscillates.

According to the third embodiment, the force control loop 28 is set suchthat the force sensor signal detected by the force sensor 1 oscillatesin a state where the contact portion of the force sensor 1 contacts thesurface of the workpiece. The scanning measurement is conducted in thisstate. Accordingly, each time the force sensor signal coincides with thecontact measuring force, the touch signal is generated from the touchsignal generator 51, and each time the touch signal is generated, thevalue of the counter 26 is latched by the latch counter 52 and thencollected by the measurement value collecting unit 55.

In other words, since the touch signal is generated utilizing theoscillating state of the force sensor signal, a high-speed touch signalcan be generated and the measuring point information can be collected atthe timing of the generation of such a touch signal, thereby realizing aprecise measurement. Particularly, since the measurement is conductedutilizing the unstable oscillation of the force control loop 28, it ispossible to stably trace the profile with tolerance to the disturbanceand to measure the workpiece including a steeply inclined surface,thereby increasing scanning speed.

Accordingly, even under the presence of the property fluctuation causedby the surface texture of the workpiece and the like and thedisturbance, the scanning measurement can be conducted with the constantmeasuring force while ensuring high precision and avoiding an increasein the measurement time.

Since the force control loop 28 is in operation when the detectionsignal from the force sensor 1 oscillates, the average value of theoscillation of the detection signal from the force sensor 1 iscontrolled to substantially coincide with the target measurement value.

Fourth Embodiment <Description of Fourth Embodiment (FIG. 7)>

Unlike the modification of the second embodiment (FIG. 5), in the fourthembodiment, the actuator 11 as the relative movement unit includes: afine feeding portion actuator 11A as a fine feeding mechanism whichfinely displaces the force sensor 1 (the measuring portion); and acoarse feeding portion actuator 11B as a coarse feeding mechanism whichdisplaces the force sensor 1 in corporation with the fine feedingportion actuator 11A by a larger amount than the fine feeding portionactuator 11A.

The fine feeding portion actuator 11A may be a drive mechanism with highresponse speed such as a piezoelectric actuator that uses apiezoelectric element. The coarse feeding portion actuator 11B may be anelectromagnetic actuator, for example.

As stated above, the scanning controller 54 of the force control loopincludes: the processing unit 23, the force control compensator 24; andthe drive amplifier 25 that amplifies the output from the force controlcompensator 24 to give the amplified output to the fine feeding portionactuator 11A and the coarse feeding portion actuator 11B. The settinggain of the force control compensator 24 of the force control loop isadjustable.

In the fourth embodiment, a coarse feeding portion controller 57 isfurther provided which traces changes in the surface profile of theworkpiece and controls the drive of the coarse feeding portion actuator11B.

Since the fine feeding portion actuator 11A and the coarse feedingportion actuator 11B are provided in the fourth embodiment, in thescanning measurement, it is possible to speedily and finely displace thecontact portion in response to fine unevenness of the workpiece surfacewith the fine feeding portion actuator 11A that has the high responsespeed, while it is possible to respond to a large profile change(undulation and the like) of the workpiece surface with the coarsefeeding portion actuator 11B capable of responding to a largedisplacement. As a result, the contact portion can be moved in ascanning manner along the workpiece surface precisely and speedily.

<Description of Modification of Fourth Embodiment (FIG. 8)>

In the fourth embodiment, the actuator 11 includes the fine feedingportion actuator 11A and the coarse feeding portion actuator 11B.However, the coarse feeding portion actuator 11B may be substituted bythe coordinate drive mechanism 40.

As shown in FIG. 8, the coarse feeding portion actuator 11B may beomitted and the coordinate drive mechanism 40 may be used to trace theprofile. In such an arrangement, the position of the force sensor 1 canbe obtained by adding the value of the detector 12 which is collected bythe measurement value collecting unit 55 (the displacement amount of theforce sensor 1) to the movement amount caused by the coordinate drivemechanism.

The arrangement of the fourth embodiment in which the fine feedingportion actuator 11A and the coarse feeding portion actuator 11Bconstitute the actuator 11 may be applied to the actuator 11 of thethird embodiment.

<Description of Modifications>

The invention is not limited to the above-described embodiments, butmodifications and improvements are also in the scope of the invention aslong as an object of the invention can be achieved.

In the above-described embodiments, the base 2 of the force sensor 1 andthe stylus 3 are integrally formed. However, the arrangement is notlimited thereto and the base 2 and the stylus 3 may be separatelyformed. The base 2 and the stylus 3 may be arranged as separatecomponents and the stylus 3 may be adhered and fixed on the base 2.

In the embodiments, the stylus 3 is adapted to oscillate in its axialdirection, but the arrangement is not limited thereto. The stylus 3 mayoscillate in a direction orthogonal to the axis of the stylus 3.

In the embodiments, the target measuring force of the scanningcontroller, the target measuring force of the force control loop and thecontact measuring force of the touch signal generating unit areindividually explained. However, those measuring forces may be the sameas a value.

In the embodiments, an example is shown in which the positionmeasurement value from the counter 26 (the measuring point information)is collected at a predetermined time interval, but the arrangement isnot limited thereto. The position measurement value may be collected ata predetermined positional interval or using both of the predeterminedtime and positional intervals.

In the first embodiment (FIG. 1), an arrangement in which the actuator11 is provided is exemplified, the arrangement is not limited thereto.The actuator 11 may not be provided. In this case, the scanningcontroller 54 controls the coordinate drive mechanism 40 (the X, Y and Zaxes) and the measurement value collecting unit 55 collects, as themeasurement value, a value obtained by adding the displacements of theaxes (for example, the displacements along the X, Y and Z axes) of thecoordinate drive mechanism to the position measurement value from thecounter 26 or to the position measurement value of the latch counter 52.

In the embodiments, the coordinate drive mechanism 40 controls the threeorthogonal axes of the X, Y and Z axes, but the arrangement is notlimited thereto. A two-dimensional drive mechanism or a one-dimensionaldrive mechanism may be alternatively employed. Further, the drivemechanism is not limited to the directly moving type but may be arotational movement type. In short, any arrangement may be employed aslong as the probe 10 and the workpiece can be relatively driven anddriving amounts thereof can be detected.

In the embodiments, the stylus that oscillates in its axial direction isused, but a sensing pin of the invention is not limited to that type andmay have an arrangement shown in FIG. 9 for example.

A sensing pin 90 is provided to a drive movable portion of the actuator11 (or the fine feeding portion actuator 11A and the coarse feedingportion actuator 11B) via an elastic lever 91 that is elasticallydeformable in a direction along an operation direction of the actuators,a longitudinal direction of the elastic lever 91 being substantiallyorthogonal to the operation direction of the actuators. When the sensingpin is brought into contact with the surface of the workpiece, themeasuring force applied between the workpiece and the sensing pin 90causes an elastic deformation of the elastic lever 91. Accordingly,changes in the measuring force can be obtained by detecting an amount ofthe elastic deformation of the elastic lever 91. For example, adetecting unit for the elastic deformation amount of the elastic lever19 may be a distortion sensor or a detector 94 that irradiates a laserbeam 92 to an upper surface of the elastic lever 91 and detects theelastic deformation amount of the elastic lever 91 based on reflectedlight 93 from the upper surface.

The priority application Number JP 2006-157870 upon which this patentapplication is based is hereby incorporated by reference.

1. A surface texture measuring instrument, comprising: a measuringportion including a stylus having a contact portion that contacts asurface of a workpiece and a measuring force detecting unit that detectsa measuring force when the contact portion contacts the surface of theworkpiece; a relative movement unit that relatively moves the measuringportion and the workpiece; a position detecting unit that outputs asmeasuring point information a measuring point on which the workpiece ismeasured by the measuring portion, the measuring point information fromthe position detecting unit being collected while the relative movementunit is driven with the contact portion of the stylus contacting thesurface of the workpiece, a surface texture of the workpiece beingmeasured from the measuring point information, a scanning controllerthat collects a detection measuring force from the measuring portion anddrives the relative movement unit such that the detection measuringforce substantially coincides with a target measuring force; a touchsignal generating unit that collects the detection measuring force fromthe measuring portion and generates a touch signal when the detectionmeasuring force coincides with a contact measuring force; and ameasurement value collecting unit that collects the measuring pointinformation from the position detecting unit based on a predeterminedcondition when a fluctuation range of the detection measuring force fromthe measuring potion is within a preset certain range, the measurementvalue collecting unit collecting the measuring point information fromthe position detecting unit each time the touch signal is generated fromthe touch signal generating unit when the detection measuring force fromthe measuring portion oscillates and an oscillation range exceeds apreset certain range, when the scanning controller is in operation.
 2. Asurface texture measuring instrument, comprising: a measuring portionincluding a stylus having a contact portion that contacts a surface of aworkpiece and a measuring force detecting unit that detects a measuringforce when the contact portion contacts the surface of the workpiece; arelative movement unit that relatively moves the measuring portion andthe workpiece; a position detecting unit that outputs as measuring pointinformation a measuring point on which the workpiece is measured by themeasuring portion, the measuring point information from the positiondetecting unit being collected while the relative movement unit isdriven with the contact portion of the stylus contacting the surface ofthe workpiece, a surface texture of the workpiece being measured fromthe measuring point information, a scanning controller that collects adetection measuring force from the measuring portion and drives therelative movement unit such that the detection measuring forcesubstantially coincides with a target measuring force; a touch signalgenerating unit that collects the detection measuring force from themeasuring portion and generates a touch signal when the detectionmeasuring force coincides with a contact measuring force; a switch unitthat switches a scanning measurement mode and a touch measurement mode;and a measurement value collecting unit that collects the measuringpoint information from the position detecting unit based on apredetermined condition when the switch unit is switched to the scanningmeasurement mode, the measurement value collecting unit collecting themeasuring point information from the position detecting unit each timethe touch signal is generated from the touch signal generating unit in astate where the switch unit is in the touch measurement mode, when thescanning controller is in operation.
 3. The surface texture measuringinstrument according to claim 2, wherein the switch unit includes aswitch portion that switches between the scanning measurement mode andthe touch measurement mode in accordance with a surface profile of theworkpiece based on a selection made by a user.
 4. The surface texturemeasuring instrument according to claim 2, wherein the switch unitincludes a switch portion that switches between the scanning measurementmode and the touch measurement mode and a switching controller thatcontrols the switch portion, and the switching controller switches theswitch portion based on change in the detection measuring force detectedby the measuring force detecting unit.
 5. The surface texture measuringinstrument according to claim 2, wherein the switch unit includes aswitch portion that switches between the scanning measurement mode andthe touch measurement mode and a switching controller that controls theswitch portion, and the switching controller switches the switch portionbased on the surface profile of the workpiece.
 6. The surface texturemeasuring instrument according to claim 1, wherein the scanningcontroller includes a processing unit that computes a deviation betweenthe detection measuring force from the measuring portion and the targetmeasuring force and outputs the deviation; and a gain adjusting unitthat amplifies an output signal from the processing unit and gives theoutput signal to the relative movement unit, and the setting gain of thegain adjusting unit is adjustable such that the detection measuringforce from the measuring portion oscillates.
 7. The surface texturemeasuring instrument according to claim 2, wherein the scanningcontroller includes a processing unit that computes a deviation betweenthe detection measuring force from the measuring portion and the targetmeasuring force and outputs the deviation; and a gain adjusting unitthat amplifies an output signal from the processing unit and gives theoutput signal to the relative movement unit, and the setting gain of thegain adjusting unit is adjustable such that the detection measuringforce from the measuring portion oscillates.
 8. The surface texturemeasuring instrument according to claim 1, wherein the relative movingunit includes: a fine feeding mechanism which finely moves the measuringsection; and a coarse feed mechanism which moves the fine feedingmechanism and the measuring section more coarsely than the fine feedingmechanism, the scanning controller includes the processing unit thatcomputes the deviation between the detection measuring force from themeasuring portion and the target measuring force and outputs thedeviation; and the gain adjusting unit that amplifies an output signalfrom the processing unit and gives the output signal to the fine feedingmechanism, and the setting gain of the gain adjusting unit is adjustablesuch that the detection measuring force from the measuring portionoscillates.
 9. The surface texture measuring instrument according toclaim 2, wherein the relative moving unit includes: a fine feedingmechanism which finely moves the measuring section; and a coarse feedmechanism which moves the fine feeding mechanism and the measuringsection more coarsely than the fine feeding mechanism, the scanningcontroller includes the processing unit that computes the deviationbetween the detection measuring force from the measuring portion and thetarget measuring force and outputs the deviation; and the gain adjustingunit that amplifies an output signal from the processing unit and givesthe output signal to the fine feeding mechanism, and the setting gain ofthe gain adjusting unit is adjustable such that the detection measuringforce from the measuring portion oscillates.
 10. A surface texturemeasuring instrument, comprising: a measuring portion including a stylushaving a contact portion that contacts a surface of a workpiece and ameasuring force detecting unit that detects a measuring force when thecontact portion contacts the surface of the workpiece; a relativemovement unit that relatively moves the measuring portion and theworkpiece; a position detecting unit that outputs as measuring pointinformation a measuring point on which the workpiece is measured by themeasuring portion, a force control loop that collects a measuring forcedetected by the measuring portion and drives the relative movement unitsuch that the detection measuring force substantially coincides with atarget measuring force; a touch signal generating unit that collects thedetection measuring force detected by the measuring portion andgenerates a touch signal when the detection measuring force coincideswith a contact measuring force; and a measurement value collecting unitthat collects the measuring point information from the positiondetecting unit each time the touch signal is generated from the touchsignal generating unit, wherein the force control loop is adjustablesuch that the detection measuring force detected by the measuring forcedetecting unit oscillates.
 11. The surface texture measuring instrumentaccording to claim 10, wherein the force control loop includes aprocessing unit that computes a deviation between the detectionmeasuring force detected by the measuring force detecting unit and thetarget measuring force and outputs the deviation; and a gain adjustingunit that amplifies an output from the processing unit by a setting gainand gives the output to the relative movement unit, and the setting gainof the gain adjusting unit of the force control loop is adjustable suchthat the detection measuring force detected by the measuring portionoscillates.
 12. The surface texture measuring instrument according toclaim 10, wherein the relative moving unit includes: a fine feedingmechanism which finely moves the measuring section; and a coarse feedmechanism which moves the fine feeding mechanism and the measuringsection more coarsely than the fine feeding mechanism, the force controlloop includes a processing unit that computes a deviation between thedetection measuring force detected by the measuring force detecting unitand the target measuring force and outputs the deviation; and a gainadjusting unit that amplifies an output from the processing unit by asetting gain and gives the output to the fine feeding mechanism, and thesetting gain of the gain adjusting unit of the force control loop isadjustable such that the detection measuring force detected by themeasuring portion oscillates.
 13. The surface texture measuringinstrument according to claim 1, wherein the touch signal generatingunit generates a touch signal when the detection measuring force fromthe measuring portion passes the contact measuring force from a valuehigher than the contact measuring force and when the detection measuringforce from the measuring portion passes the contact measuring force froma value lower than the contact measuring force.
 14. The surface texturemeasuring instrument according to claim 2, wherein the touch signalgenerating unit generates a touch signal when the detection measuringforce from the measuring portion passes the contact measuring force froma value higher than the contact measuring force and when the detectionmeasuring force from the measuring portion passes the contact measuringforce from a value lower than the contact measuring force.
 15. Thesurface texture measuring instrument according to claim 10, wherein thetouch signal generating unit generates a touch signal when the detectionmeasuring force from the measuring portion passes the contact measuringforce from a value higher than the contact measuring force and when thedetection measuring force from the measuring portion passes the contactmeasuring force from a value lower than the contact measuring force. 16.The surface texture measuring instrument according to claim 1, whereinthe measuring portion includes: an oscillation element that oscillatesthe stylus; and a detection element that detects an oscillation of thestylus and outputs a detection signal.
 17. The surface texture measuringinstrument according to claim 2, wherein the measuring portion includes:an oscillation element that oscillates the stylus; and a detectionelement that detects an oscillation of the stylus and outputs adetection signal.
 18. The surface texture measuring instrument accordingto claim 10, wherein the measuring portion includes: an oscillationelement that oscillates the stylus; and a detection element that detectsan oscillation of the stylus and outputs a detection signal.